Within Teamwork Projects, you can lock a notebook while you are editing it so nobody else can edit the notebook at the same time.

To lock a notebook, go to the Notebooks tab of your project:

Hover over the notebook you want to edit, and you will see the edit option:

When the notebook is open, you will have an option to lock the notebook, in the top right corner:

Once you have locked the notebook, you will see the following message. Once you save any changes, you will have an option to unlock:

While the notebook is locked, if other users open the notebook, they will see a message telling them it is locked for editing:

For more information, see: Creating a notebook